Research and development has been widely carried out on a region extraction technique with which a region of a moving object in an image is extracted from the image including an image of the moving object (hereinafter referred simply to as “moving object”). The technique of extracting a region of a moving object is, particularly when the moving object is a person, a fundamental technique used widely in common for: focus control and image quality improvement processing for digital video cameras or digital still cameras; image quality improvement processing; image synthesis processing for movie production; safe driving support system for vehicles; or prediction of human behavior, operating analysis, and so on. The technique of extracting a region of a moving object in an image includes, as a general method, a method of detecting a region of a moving object by evaluating the similarity between a moving object model prepared in advance and a candidate region for the moving object in the image.
The method includes, as a representative method, a method of extracting a candidate of a moving object region from an image, and then evaluates the similarity between the candidate of a moving object region that has been extracted and a moving object model prepared in advance to extract a region with high similarity as the moving object region. Furthermore, for extracting a region of a moving object which walks changing shape, such as a walking person or the like, another method using a moving object model considering shape change is used.
According to a method described in Patent Literature (PTL) 1, for example, a silhouette image of a moving object is extracted from plural images, as a candidate for a moving object region. PTL 1 further discloses a method of evaluating the similarity between a model related to a change in shape of the moving object that has been parameterized in advance and the silhouette image that has been extracted, so that a parameter of a region with high similarity and the model are estimated. Since this allows applying the parameterized model to a human figure that moves periodically changing shape, it is possible to perform extraction of a region of the moving object such as a human.
In addition, an image analysis method for extracting more detailed motion data or a shape from an image is proposed in order to generate an image of an articulated object such as a human.
For example, PTL 2 discloses further estimating, based on rough motion information of an articulation and a part which is obtained by applying a previously held model having an articulation to an articulated object in an obtained image, a position and the motion information of the articulation and the part in more detail. This allows generating a new image in which information including the shape and motion of a part of an articulated object in an image is reflected. Compared to the case where only the parameter calculated in advance is used, parameterization of the shape and motion of the part of a person in the image is made possible with higher accuracy because information is extracted from the articulated object in the image. This makes it possible to apply the parameterized model with higher accuracy also to the person that moves changing shape, thereby allowing extraction of a region of the moving object with higher accuracy.